Which one of the following is most sensitive to environmental change?

Which one of the following is most sensitive to environmental change?

Amphibian
Reptile
Mammal
Insect
This question was previously asked in
UPSC CDS-2 – 2016
Amphibians are generally considered most sensitive to environmental change among the given options.
Amphibians are particularly vulnerable to environmental changes due to several factors: their permeable skin readily absorbs substances from the environment (water and air), they often rely on both aquatic and terrestrial habitats during their life cycle, and many have specific requirements for reproduction and development. These characteristics make them highly susceptible to changes in water quality, habitat destruction, pollution, and climate change, serving as important bioindicators.
While reptiles, mammals, and insects are also affected by environmental changes, amphibians’ unique physiological and life-cycle traits often make them among the first groups to show negative impacts from habitat degradation and pollution.